1. Field of the Invention
This invention relates generally to a spring rewound tagline device as conventionally employed on cranes, and the like, to maintain tension on a tagline connected to a material handling device, such as a bucket, grab, magnet, and the like, operated by the crane so as to prevent erratic movement of the material handling device, and more particularly relates to unique means for preventing overloading of the tagline rewind spring.
2. Description of the Prior Art
U.S. Pat. Nos. 2,303,002, issued Nov. 14, 1942 to William Ruddock; 2,645,432, issued July 14, 1953 to H. V. Griffitts; and 3,062,479, issued Nov. 6, 1962 to H. V. Griffitts, disclose tagline rewind devices of the general character in which the present invention is utilized.
Briefly, these tagline devices include a reel about which a tagline is wound. The reel is rotatably supported on a shaft which is connected to a rotatable core structure positioned within an elongated cylindrical housing. A coiled torsion spring is disposed about a central core structure coaxially within the housing, one end of this spring being fixedly anchored as by a connection to the housing, while the other end of the spring is connected to the rotatable core structure. As thus arranged, rotation of the reel in a direction to payout the tagline will cause the spring to become wound or tensioned so as to resiliently rewind the reel in the opposite direction as the load on the tagline is relieved.
A difficulty encountered with these conventional and commonly employed tagline devices, as exemplified in the above U.S. patents, is that the ordinary use of a crane may, for example, swing the grab, bucket, magnet, and the like, being manipulated by the crane such a great distance as to excessively wind-up the torsion spring to such an extent as to produce an "overloading" of the spring, which could either break the spring or cause it to become immobilized by being "frozen" about the core structure of the tagline device. Thus, it becomes necessary to disassemble the tagline device in order to replace the damaged spring, and if the spring has become frozen due to the overload, it is additionally necessary to burn the spring, as through a coil or coils with a suitable acetylene torch and the like, until the spring releases its tension and unwinds. As can be appreciated, not only is the downtime of the crane and the man hours required for replacing a spring prohibitively expensive, but the cost of a replacement spring itself is a significant expense.